I've stayed at all three All-Stars, some multiple times. I'll give a few thoughts, but if you're interested in something in particular, just let me know.
Sports is the first one you come to, which can be an advantage on buses at times when the three All-Stars are all coverd by one bus.
The rooms are what they are, basic and functional, but nothing more. Buildings are small than at Pop (three instead of four stories, and a few less room per floor), but generally the same. The food court is functional, but can get really crowded, and thus slow, at mealtimes or whenever a youth group descends on it. Surf pool is quite nice, and the baseball smaller pool as a lot of fun as well.
In my experience, Sports can be quite loud at night, especially in the inner courtyard of the football buildings. If you're in the back of the place, the walk to food court/main building can be a long one.
In the category of little known facts, there's a walking path from Sports, past McDonalds, Winter/Summerland, Blizzard Beach, and some wetlands to Coronado Springs.
Since you're doing free dining, you probably will be heading to other resorts often. If you won't have a car, your best transfer point to get to other resorts is likely DHS, as it's a relatively short ride and won't involve much backtracking to get to wherever you're going. Of course, if you're headed to AKL, transfer at AK.
If you have any other questions, just ask!